Problem: $ { {5} \times \left[\begin{array}{rr}{0} & {1} \\ {-2} & {3} \\ {1} & {2}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{5}\times{0} & {5}\times{1} \\ {5}\times{-2} & {5}\times{3} \\ {5}\times{1} & {5}\times{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{0} & {5} \\ {-10} & {15} \\ {5} & {10}\end{array}\right]}$